Vinyl chloride and vinylidene chloride polymers are known to be self-extinguishing and relatively more flame retardant than other polymers such as polyethylene, polypropylene and the like. However, a substantial amount of smoke may be produced upon exposure of vinyl chloride and vinylidene chloride polymers to a flame. Conventional flame retardants such as antimony oxide do not aid in smoke reduction.
The following prior art is related to the present invention. Nickel oxides or bismuth oxides are effective in amounts up to several percent as condensing agents for polyvinyl halides. (U.S. Pat. No. 2,157,997). Bismuth oxide is a known vinyl chloride polymer flame retardant, either alone or mixed with certain other materials; see U.S. Pat. No. 2,590,211, U.S. Pat. Off. Def. Publ. 892,010 (76 Chem. Abs. 73666a), 2 Brit. Polym.J. 249-253(1970) (73 Chem. Abs.131605f), and Germ. 1,201,544 (63 Chem. Abs. 15.61e). Bi.sub.2 S.sub.3 is a known vinyl chloride polymer flame retardant (U.S. Pat. No. 2,590,211). The fact that an additive is a flame retardant does not mean that it will have good smoke retardant properties, as is well known to those skilled in the art. New smoke retardant vinyl chloride and vinylidene chloride polymer compositions are desired.